1. Field of the Invention
This invention relates to vending machine control systems using magnetically encoded readable/writeable cards as a medium of exchange. In particular, the invention relates to techniques and means for preventing the registration of false information on the magnetic cards and to prevent abuse of the information on the magnetic cards.
In the past, two particular problems have existed with respect to magnetic card accounting systems. First, card users have occasionally attempted to withdraw the magnetic card from the reader/writer before the registration of updated accounting information on the magnetic stripe of the card in order to be able to reuse the card. The structure of magnetic card reads is such that the updating information is intended to be recorded on the card as it is ejected from the reader/writer. In the past, it has therefore been possible to withdraw the card prior to updating by, for example, placing a piece of tape on the card and manually pulling the tape and card out of the reader/writer.
Second, vending machine power sources are subject to interruption, either accidentally or intentionally. Accidental power interruption may occur whenever there is a main power failure. Intentional interruption may be the attempt of someone to stop machine operation prior to the recording of updating information in order to prevent the card value from being updated. Means and techniques are needed to cope with these common problems to assure security and reliability of a vending machine accounting system.
2. Brief Description of the Prior Art
Heretofore, power source interruption has been guarded against by providing a battery backup to the memory elements of the control systems of a duplicator controller.